Increasingly, electronic card systems using magnetic or otherwise coded cards and slide type readers have been used to replace mechanical locks. These are relatively expensive, both in capital costs and in frequency of maintenance.
One problem associated with key operated locks is the difficulty of re-keying the lock. If a key is lost or stolen, a locksmith is required to provide a set of new keys and alter all the common-keyed locks. Mechanical card locking systems are known from e.g. U.S. Pat. No. 4,149,394 (Sornes), which utilise a card having round holes therein. The card can be inserted into the lock, whereby biased ball bearings are displaced. It the ball bearings are displaced in a predetermined manner, the lock can be opened. A similar ring-operated lock is disclosed in U.S. Pat. No. 4,338,805 to Nygren. These arrangements all subject the card to considerable wear, and allow for operation from one side only. Further, they cannot be readily re-keyed, nor do they allow for the use of a magnetic strip in addition to the mechanical mechanism. Such arrangements only allow for one possible position for each ball or ring, and do not allow for master keying hierarchies.
U.S. Pat. No. 4,627,252 (Lo) discloses a card operated lock using a set of plates arranged to directly receive a card with notches selectively removed in the end. This lock is only operable from one side, and re-keying involves rearranging the plates. The user card directly engages the lock mechanism. This arrangement only allows for one possible position for each ball or ring, and does not allow for master keying hierarchies.
French Patent Specification No. 1,163,526 (Beaudelet) discloses a simple mechanical lock arrangement comprising a series of spring loaded locking tumblers which are capable of being displaced independently of one another in a plane perpendicular to that in which the slide bolt is displaced. The mechanism is operable by use of a key featuring a series of grooves of varying depths, witn one groove provided for each tumbler. Upon insertion of the key the tumblers undergo varying displacements, with the correct combination of displacements leading to the unlocking of the mechanism. However this mechanical lock arrangement does not allow for the re-keying of the lock mechanism.
U.S. Pat. No. 2,692,495 (Verdan) discloses a complex mechanical lock arrangement operable using a user card including a pattern of holes and a combination card to define a combination for the lock mechanism. Unlocking of the mechanism is achieved the pattern of holes in the user card matches those on the counter key. However whilst this arrangement does enable the rekeylng of the lock mechanism, it is a complex arrangement which would be difficult to manufacture and which would require frequent maintenance in order to provide satisfactory and consistent working performance.
It is therefore an object of the present invention to provide a mechanical card lock which overcomes at least partly, the disadvantages of the prior art.